Research Of Tube-Tubesheet Hydraulic Expansion Technology Of Nuclear Steam Generator

Our country to develop nuclear power is an important energy policy, nuclear power plant steam generator as key equipment, and its importance is self-evident. The quality of the joint of tube and tubesheet is the key factor that affects the service life of steam generator on site. The hydraulic expansion technology is one of the key manufacturing technologies of steam generator. Research on the hydraulic expansion technology is very important to improve the quality of steam generator and keep the nuclear power plant safe operation in lifetime.Based on the heat transfer tube and tube sheet corrosion mechanism in this paper, as well as a number of factors affecting hydraulic expansion as the basic theoretical research, starting from the production process, the author explored the main process parameters affect the nuclear steam generator hydraulic expansion of product quality. This paper explores the main factors that could affects the quality of hydraulic expansion in the steam generator manufacturing of CPR1000, AP1000, EPR models. Selection and verification of hydraulic tube expander,determine expansion pressure,expansion length control technology,expansion length detection method, eddy current testing technology in the manufacture of steam generator and residual stress of tube- tubesheet joints are also conducted. The system of hydraulic expansion technology that could be performed on the industrialization manufacturing has been obtained. The technology measures of hydraulic expansion in manufacturing to assure the quality of steam generator has been finally worked out by the author.To determine hydraulic expanding machine is difficult due to few steam generator expansion application nationwide, therefore the author conducted study on expansion structure and expansion pressure based on calculation and product trail test. It is found that the expansion length has effect on the controlling inflation and the hydraulic fluid type of oil, water, gas three-loop hydraulic tube expander, and the expansion of rigid rod-type O-ring structure were found the best expansion equipemnt for the steam generator tube to tubesheet expansion.With the comparison on the advantages and disadvantages of internal diameter measurement with dial indicator, microscopic observation on cutting cross section and eddy current testing method as well as investigation on inspection work required and implemented with eddy current testing method, eddy current testing method has been determined as the steam generator tubes to tubesheet joints expansion length measurement method. Finally inspection technical parameters and sample calibration procedures have been obtained for the control of expansion length.In order to investigate effect of residual stress on corrosion of heat transfer tube to tubesheet joints, the author undertaken residual stress measurement of the heat transfer tube to tubesheet joints. X Ray residual stress test method has been proven to be the applicable for the residual stress measurement by both theoretical and experimental methods. Sectioning and blind-hole residual stress test also conducted to compare with the X Ray method for the tube to tubesheet joint residual stress test. It is concluded that all three testing methods are applicable for the residual stress testing of tube to tubesheet expansion joints and therefore all the methods are used by the author during the practical production of steam generators.